Neo acids are difficult to esterify by common techniques due to the steric effects of the alpha-carbon alkyl groups. Nevertheless, many methods have been disclosed for manufacturing neo acid esters.
Coopersmith, et al., Preparation and Hydrolytic Stability of Trialkylacetic Acid Esters, I&EC Product Research and Development, Vol. 5, No. 1 (1966), report that neo acids are esterified using an acid catalyst to increase the rate of the esterification reaction, and an entrainer and molecular sieve to remove water produced during the esterification reaction. The study also reports that the rate of esterification can be adjusted by varying the type and concentration of the catalyst and by selection of the entrainer. This report specifically concentrates on esterification reactions involving neo-pentanoic acid and neo-heptanoic acid.
U.S. Pat. No. 4,332,738 to Benitez et. al. closes a process for direct esterification of a neo acid (having 5 to 28 carbon atoms) with an alcohol in a non-aqueous system in the presence of a macro-reticular structured sulfonic acid cation exchange resin. This process allows esterification under mild conditions (50° C. to 70° C.) by mixing stoichiometric amounts of the desired reactant neo acid with the desired reactant alcohol. The preferred neo acids include neo-pentanoic acid and neo-decanoic acid.
In general, conventional neo acid esterification processes require complex purification procedures, prior to the esterification reactions, to obtain the required neo acid for esterification. Reducing the need for these prior purification procedures would be valuable in saving time and energy and in reducing overall manufacturing complexity and cost. Accordingly, new neo acid esterification processes are desired.